1. Field of the Invention
The present invention relates to an actuator for a door lock mechanism used for, for example, an automobile.
2. Prior Art
In conventional door lock system actuators of this type, a motor power is transmitted via a worm gear to a rotary disc that has a spiral guide. The spiral guide of the rotary disc shifts the position of one end of a rotatable lever, thus causing the other end of the rotary lever to actuate a latch mechanism that locks and unlocks the door.
In this conventional actuator, the spiral guide must be gentle in its curvature in order to increase the driving force that is transferred to the rotary lever. When the curvature of the spiral guide is gentle, however, the magnitude of displacement (stroke quantum) of the rotary lever relative to the rotation angle of the rotary disc becomes small. Accordingly, in order to secure a strong driving force as well as the required stroke quantum, it is inevitable to design the rotary disc large in diameter, which contrarily, results in a proportional enlargement of the actuator as a whole. Besides, the rotary disc is designed to stop after being positionally shifted; as a result, one end of the rotary lever is kept in contact with the spiral guide. If, in this state, an attempt is made to manually operate the door lock latch mechanism, it demands a strong force because the motor side, relative to the rotary lever, works as a load.